I'm new to TD (3.3) and I was wondering if it is possible to change the layout of the Seating Chart in the Tournament window - as it is possible in the Seating Chart window?

If you select the Layout tab it is possible to add the Seating Chart to the window - e.g. under the clock.

In the Properties/Contents of the Seating Chart element the following appears: <seatingchart format="diagram" columns="2">

I was wondering what other formats/properties are allowed here, since I would like to display the following image/template instead: <datastore>\templates\RacetrackEightSeatTableBlueprintLarge.xml (as in the Seating Chart window)

There are indeed other properties. Edit the Seating Chart cell by double-clicking it in the Layout tab. Click on Contents to edit the contents. You should see an editor with:

<seatingchart format="diagram" columns="2">

Highlight (select) part of that text and then press the Insert Token button. The editor should realize you've got part of a token highlighted, and highlight the entire token text for you. Then the Token Builder dialog will open, and the seatingChart token will already be selected. This dialog lists all of the available tokens that can be inserted into your layout, all of their attributes and options, and has descriptions for everything. You can make changes to the token's attributes, and when you press the OK button when done, it will insert the correct token back into the cell contents.

Near the bottom of the dialog is also a Cheat Sheet button, which will open a cheat sheet in your default browser. This lists all of the tokens, their descriptions, attributes, etc.